1. Field of the Invention
The present invention relates to an incident illumination unit provided to an illumination device for incident fluorescence observation used in a bioresearch field and a microscope to which an incident illumination unit is applied.
2. Description of the Background Art
In the incident fluorescence observation used in the bioresearch field, for instance, there is a case that the illumination with a specific wavelength is irradiated only to the specific area (minute area) other than the observation area. For instance, there is a case of irradiating the specific wavelength to perform a Caged release, and, in this case, the incident illumination device has a function to irradiate a specific area different from the incident illumination, usually.
As means for irradiating the illumination only to such a specific area (minute area), a method of arranging a stop to a conjugate position to the sample and projecting a stop shape to the sample surface is usually adopted. In the illumination device for general incident fluorescence observation, the field stop which is arranged to the conjugate position to the sample, can adjust the stop diameter, and comprises a centering mechanism which can be positioned on the illumination axis is built in.
Such a field stop mechanism is disclosed in the Japanese Utility Application KOKAI Publication No. 6-23017. The field stop has a configuration in which the field stop moves along the direction of the illumination axis by synchronizing with the stop diameter adjustment. This is aimed to correct the field stop image blurring according to the stop diameter change which occurs because of the aberration of the lens group (Hereafter, called as a, “FS projection lens group”) to project the field stop to the sample side, and to project the stop on the sample side strictly.
Moreover, the stop which can adjust the stop diameter similarly and can adjust the centering is disclosed in the Japanese Patent Application KOKAI Publication No. 10-73768 though it is not a field stop, and the illumination axis direction position of the stop is changed by configuring the stop as a unit, and reversing the direction of the installation of the unit.
However, the field stop mechanism is integrally provided to a part of the incident illumination system etc. inside the microscope in the technology described in the Japanese Utility Application KOKAI Publication No. 6-23017. Therefore, an arbitrary stop (element) which is requested by the user cannot be arranged on the incident illumination axis. In a word, the stop shape of a built-in the microscope variable diameter is only a circle and a minimum diameter of this kind of stop is generally limit to 0.5 mm to 1 mm, therefore it is difficult to narrow the diameter to a more minute area. Therefore, the stop of a minute diameter which satisfies the request of the user cannot be easily arranged on the incident illumination axis.
Moreover, if the aberration by the wavelength of the illumination is not considered in addition to the aberration of the FS projection lens to use the illumination of a variety of wavelength band in the incident fluorescence illumination, and the field stop cannot be projected to the sample surface strictly. In the technology described in the Japanese Utility Application KOKAI Publication No. 6-23017, it is not possible to correspond to the adjustment against besides the aberration of such FS projection a lens.
In addition, the stop cannot be inserted and withdrawn in the technology described in the Japanese Utility Application KOKAI Publication No. 6-23017 to the illumination path. Therefore, when a whole image is observed by the illumination with a different wavelength band after the wavelength band in a specific range of the sample for instance is illuminated, it is necessary to change the stop diameter during the observation. Therefore, when this work is repeated, annoying work of adjusting the stop diameter in every case within the specific range is occurred.
Moreover, the technology of the Japanese Patent Application KOKAI Publication No. 10-73768 has the problem that the direction of the illumination axis and the position of the stop cannot be continuously adjusted in addition to a similar problem as mentioned above. Therefore, the user cannot accurately arrange the stop at an arbitrary position.